Aerodynamic control for sailing vessels



April 16, 1963 J. RABINOW ETAL 3,085,534

AERODYNAMIC CONTROL FOR SAILING VESSELS Filed March 28, 1962 INVENTORS Jacob Rab/now Harold J. Rosenberg W a. flwm BY 7444 a. f

ATTORNEYS States nite This invention relates to sailing craft, and particularly to an aerodynamic aid for sailing, especially when there is a crisp cross wind.

Our invention is concerned mainly with stabilizing a sailing craft by preventing heeling although, as will be seen later, there are other inherent advantages. There have been prior efforts to stabilize sailing craft (apart from a keel), and these have been directed toward overcoming instability by two methods. The first is to provide ballast on the sides of the sailing craft such as disclosed in US. Patents No. 543,210; and 1,371,139. The earlier of these patents discloses that it has been common to provide a lee-board hinged or fixed to the side of the vessel to contact the water when the vessel heels. This patent points out advantages in substituting airtight shelves for the lee-boards. These shelves are hinged to the sides of the boat and can be made to contact the water. When the hinges are locked, the shelves function as outrigger pontoons. The effect is to limit heeling, in contrast to preventing heeling which is an aim of our invention.

The other method of solving the same problem is to use pontoons of various configurations and designs. For example, US. Patents No. 1,709,219 and 2,756,711 disclose two different ways of relying on outrigger pontoons to stabilize a sailing vessel. In both arrangements, the pontoons remain in the water and hence, they produce hydrodynamic drag.

Although physical embodiments of our invention resemble outrigger pontoons, the resemblance is only superficial. We have observed that heeling of a sailing vessel is ordinarily caused by cross winds, and we have made the further observation that the same cross winds could be used to generate aerodynamic lift to either attenuate or substantially eliminate heeling. By relying on aerodynamic forces we eliminate a serious difiiculty encountered in using outrigger pontoons for the same purpose. In brief, we avoid all of the hydrodynamic features of outrigger pontoons including hydrodynamic drag. Furthermore, should an outrigger pontoon stabilizer bufiet, the sailing vessel is subjected to erratic torsional forces due to the successive engagement and disengagement of the outrigger pontoon with the water. The torsional forces referred to are those caused by the hydrodynamic drag at the time that the pontoon engages the water, this force having a reaction in the boat itself tending to turn the boat about a vertical axis passed through the pontoon.

Our invention, which relies on aerodynamic forces instead of buoyance of a pontoon, has no reliance whatsoever on the water to obtain a reaction. Instead, we rely on the same cross wind which tends to cause the vessel to heel, to produce lift which acts through a moment arm in the proper direction to overcome the heeling tendency of the vessel.

Since we rely on aerodynamic moments to take the place of outboard stabilizing pontoons and/or the usual practice of the sailor (or crew) leaning to the port or starboard side, our invention provides additional advantages. We can rely on the same lift-producing feature to cause the vessel to be effectively lighter in the water. If the total weight of the vessel and crew is comparatively small, it is possible to obtain enough aerodynamic lift to appreciably reduce the draft of the vessel. With largearea airfoils having a reasonable lift coefficient and with crisp winds, for instance, of the order of 25 to 30 knots, enough aerodynamic lift can be produced to have the boat operate in a skimming mode.

Accordingly, another object of our invention is to provide aerodynamic lift producing means for a sailing vessel, which relies on the wind velocity to produce lift in such a way as to produce moments which prevent or at least attenuate heeling.

A further object of the invention is to provide an aerodynamic lift-producing device for a sailing vessel where the lift can be directed in such a way as to reduce the draft of the vessel.

In the simpler form of our invention, which has been selected for illustration, We have two outrigger airfoils whose lift acts through moment arms to exert reaction forces on the vessel in the desired direction. A feature of our airfoil arrangement is that the airfoils can be adjusted so that the sailor can select both the magnitude and direction of lift which he desires. This is to enable the sailor to take advantage of the aerodynamic lift producing device regardless of whether it is desired to execute a turn in either direction.

To our knowledge, no one has, in the past, relied on aerodynamic forces to help stabilize a sailing vessel in the manner which is disclosed herein, although there has been efiiort along these lines by relying on shifts in ballast or the crew shifting its weight or outrigger pontoons. None of these methods provide the above discussed advantages of our invention. In addition, at low (compared to airplane flight) wind speeds encountered in sailing, the magnitude of aerodynamic lift is proportional to wind speed. Thus, the more that a cross wind tends to heel a vessel, the greater the aerodynamic restoring force. Also, by having the airfoils adjustable, the sailor is able to select the amount of lift (restoring force on the vessel) which he desires (within the parameter of available lift). This preserves an element of sailing skill.

Other objects and features of importance will become apparent in following the description of the illustrated forms of the invention.

FIGURE 1 is an end elevational view of a conventional sailing vessel equipped with our device.

FIGURE 2 is a top view of the vessel in FIGURE 1,

with the sail omitted.

FIGURE 3 is a schematic perspective view of a typical control system for our airfoils.

FIGURE 4 is a fragmentary perspective view showing a modification.

In the accompanying drawing FIGURE 1 shows a conventional, small sailing vessel 10. The sailing vessel has a hull 12, a deck 13, a mast 14 with its sail 16, and a keel 18.

Our aerodynamic lift-producing device is composed of airfoils 20 and 22 having their spans lengthwise of the center line of the vessel. This arrangement is not critical and, in fact, to obtain a lift component when the vessel is moving forward, and the wind is essentially fore and aft, the airfoils could be arranged with a sweep angle relative to the longitudinal center line of the vessel. They could also be tilted fore and aft so that the lift forces will have forward components. The airfoil selection is made to satisfy the criterion that the airfoil shall produce lift when the wind direction is from the front to rear edge of the airfoil orvice versa. Practically all aircraft airfoils satisfy this requirement, although not particularly efliciently. An airfoil having symmetrical leading and trailing portions (as shown or with a straight lower surface) is satisfactory. Assuming a reasonable lift coefficient and a comparatively large area, such as shown in FIGURE 2, and wind velocities of the order mentioned,

several hundred pounds of lift will be reasonably available. This lift, operating through a moment arm of, for instance, 8 to 10 feet, will provide considerably more force to attenuate or prevent heeling than is available by relying on the usual crew-shifting methods. Furthermore, although not shown, we could use either biplane or triplane airfoil assemblies with or without stagger to somewhat increase the total available aerodynamic lift.

Our airfoils and 22 can be mounted as outriggers by any of the methods disclosed in the referred-to prior patents. In addition, we could use the deck of the vessel as shown in FIGURE 2, by providing clamps 24 and 26 to which lateral support arms 28 are rigidly, removably or hingedly fixed. If a hinge connection is used there is the advantage of being able to swing the airfoils vertically up when they are not used, but the hinges would have to be locked when the airfoils are in the operative position (FIGURES 1 and 2). FIGURE 4 shows a further altemative where one of the arms 28a is attached by a clamp 24a to the gunnel of the vessel. The kind of clamp structure used for physical attachment of my device to the vessel is not of particular consequence.

Our airfoils could be rigidly attached to the outrigger arms 28 after selection of a compromise angle of incidence for the airfoils which would suit most purposes. However, an advantage of our aerodynamic device over ordinary hydrodynamic outriggers is that the sailor can more closely approximate the sailing skill required as the sailor shifts his weight during sailing. We achieve this aerodynamically by having the airfoils adjustable or by using ailerons similar to conventional airplane ailerons. If ailerons are used, their controls can be similar to the controls shown in FIGURE 3.

In FIGURE 3 the airfoils 20 and 22 are shown rigidly attached to spindles 30 and 32 whose ends are mounted in bearings at the extremities of the outrigger arms 28. Control arms 34 and 36 are fixed to the spindles and have cables or ropes 40 and 42 connected respectively to the upper and lower ends of the respective control arms and to a control stick 44. The control stick and cable assembly is the same as is used in a light aircraft for controlling the ailerons. Thus, the control stick 44 is mounted for oscillation on a pivot 46 which is anchored in the cockpit of the boat. The cables are crossed on one side of the control stick only. Thus, when a control stick is moved in one direction the airfoils will tilt clockwise and counterclockwise respectively to achieve the conditions shown in FIGURES 1 and 3. Thus, by changing the angle of incidence of the airfoils in the manner shown, magnitude of the resulting vertical component of force as shown by the vertical arrows in FIGURE 1 can be altered in accordance with the desires of the sailor.

FIGURE 2 shows a modified control arrangement Where the control stick 44a is the same as the control stick 44. The difference in construction is that the airfoils 20 and 22 of FIGURE 2 are mounted on trunnions or on a spindle which is fixed to the extremities of the outrigger arms, 28. Thus, the airfoils are capable of being rotationally adjusted, which would necessitate attaching control arms 36a and 34a to the airfoils themselves and not to spindles such as at 30 and 32 in FIGURE 3. To obtain a reasonably large angular adjustment, slots 48 and 50 are provided in the airfoils so that there is clearance for the cables.

An operating condition of our invention is shown in FIGURE 1 where the cross wind is represented by a number of horizontal arrows. With the airfoils adjusted as shown, there is a downward component of force (negative lift) generated by airfoil 20. As the wind blows across the deck of the vessel and across the airfoil 22, its angle of incidence is such that airfoil 22 produces an upward force (positive lift). Both of these forces act through moment arms established by the support arms 28. The directions of the negative and positive lift forces of the respective airfoils are in the proper direction to tend to keep the sailing vessel erect. The two forces can be thought of as a mechanical couple tending to keep the vessel righted, where the equal and opposite force to define the mechanical couple is caused by the cross wind and sail.

It is understood that various changes and modifications may be made in the invention without departing from the protection of the following claims. For example, we believe our invention to be the first method of at least attenuating (when not fully preventing) heeling, which may be embodied in a form where the device is effectively used on one side only of the sailing vessel. Where there is an outrigger pontoon on one side of the sailing vessel, the weight of the pontoon must be relied on to limit heeling when the vessel heels in one direction, and its buoyance must be relied upon when the vessel heels in the opposite direction. With our system-e.g. using airfoil 20 to the exclusion of airfoil 22, it is equally simple to produce either negative or positive lift depending on whether a clockwise or counter-clockwise tendency to heel is to be overcome.

We claim:

1. In a sailing vessel which has a sail for propulsion of the vessel and a hull together with a mast supporting the sail, the improvement comprising an aerodynamic liftproducing device having a spanwise dimension larger than the chordwise dimension, mechanical means attaching the ends of said lift-producing device outboard of the hull with the spanwise dimension of said device being in a fore and aft relationship to said hull, the aerodynamic force generated by said device and the mounting thereof on the hull establishing a moment arm through which the aerodynamic force acts on the hull, and said aerodynamic device being responsive to cross winds for producing said aerodynamic force to prevent heeling of the vessel and thereby stabilizing the vessel.

2. The subject matter of claim 1 and means to adjust the angle of incidence of said aerodynamic device by tilting said device about a spanwise axis thereof.

3. In a sailing vessel having a hull, a mast secured to the hull, and a sail attached to the mast, the improvement comprising aerodynamic means for preventing the vessel from heeling due to cross winds, said aerodynamic means including a pair of outrigger airfoils, each airfoil having a spanwise dimension greater than the chordwise dimension, a pair of support arms for each airfoil, the inner ends of each pair of arms attached to said hull, said pairs of arms projecting laterally outward from the sides of said hull, one airfoil connected to the outer ends of one pair of arms, and the other airfoil connected to outer ends of the other pair of arms, said airfoils being located at an elevation with respect to said hull that they are in a plane in the region of the lower part of said sail so that said airfoils are exposed to cross winds which ordinarily cause vessel heeling, and the aerodynamic forces generated by said airfoils and acting through said pairs of arms being in a direction which opposes vessel heeling.

4. In a sailing vessel having a hull, a mast secured to the hull, and a sail attached to the mast, the improvement comprising aerodynamic means for preventing the vessel from heeling due to cross winds, said aerodynamic means including a pair of outrigger airfoils, each airfoil having a spanwise dimension greater than the chordwise dimension, a pair of support arms for each airfoil, the inner ends of each pair of arms attached to said hull, said pairs of arms projecting laterally outward from the sides of said hull, one airfoil pivoted to the outer ends of one pair of arms, and the other airfoil pivoted to the outer ends of the other pair of arms, said airfoils being located at an elevation with respect to said hull that they are in a plane in the region of the lower part of said sail so that said airfoils are exposed to cross winds which ordinarily cause vessel heeling, the aerodynamic forces generated by said 5 6 airfoils and acting through said pairs of arms being in 3, References Cited in the file of this patent direction which opposes vessel heeling, and controlmeans UNITED STATES PATENTS including a single movably mounted control member with connecting members attached thereto and to the respective 486381 Lachmann 1892 airfoils, said connecting members arranged to cause the 5 FOREIGN PATENTS airfoils to pivot concurrently but in opposite directions in 875,617 Germany May 4, 1953 response to movement of said control member. 606,203 France 6, 1926 

1. IN A SAILING VESSEL WHICH HAS A SAIL FOR PROPULSION OF THE VESSEL AND A HULL TOGETHER WITH A MAST SUPPORTING THE SAIL, THE IMPROVEMENT COMPRISING AN AERODYNAMIC LIFTPRODUCING DEVICE HAVING A SPANWISE DIMENSION LARGER THAN THE CHORDWISE DIMENSION, MECHANICAL MEANS ATTACHING THE ENDS OF SAID LIFT-PRODUCING DEVICE OUTBOARD OF THE HULL WITH THE SPANWISE DIMENSION OF SAID DEVICE BEING IN A FORE AND AFT RELATIONSHIP TO SAID HULL, THE AERODYNAMIC FORCE GENERATED BY SAID DEVICE AND THE MOUNTING 